Pluripotent stem cells have the ability to both proliferate in culture and, under appropriate growth conditions, differentiate into lineage restricted cell types representative of all three primary germ layers: endoderm, mesoderm and ectoderm (U.S. Pat. Nos. 5,843,780; 6,200,806; 7,029,913; Shamblott et al., (1998) Proc. Natl. Acad. Sci. USA 95:13726; Takahashi et al., (2007) Cell 131(5):861; Yu et al., (2007) Science 318:5858). Defining appropriate growth conditions for particular lineage restricted cell types will provide virtually an unlimited supply of that cell type for use in research and therapeutic applications.
Protocols for differentiating primate pluripotent stem (pPS) cells into a variety of targeted cell types including oligodendrocytes, neuronal cells, cardiomyocytes, hematopoietic cells, pancreatic islet cells, hepatocytes, osteoblast and chondrocytes have been described (see, e.g., U.S. Pat. Nos. 7,285,415; 6,833,269; 7,425,448; 7,452,718; 7,033,831; 7,326,572; 6,458,589; 6,506,574; 7,256,042; 7,473,555; U.S. Patent Publication Nos. 2005/0158855; 2004/0224403; 2005/0282272; 2005/0282274; 2006/0148077; U.S. patent application Ser. No. 12/412,183; PCT Publication No. WO 07/149,182; WO 05/097980; Carpenter et al. (2001) Exp Neurology 172:383; Chadwick et al. (2003) Blood 102:906; Kierstad et al. (2005) J Neuroscience 25:4694); Laflamme et al. (2007) Nature Biotechnology 25:1015 Jiang et al. (2007) Stem Cells 25:1940.
Differentiation of pPS cells into a target phenotype cell may result in production of a mixed population of cells comprising the targeted phenotype as well as various extraneous phenotypes. Certain extraneous phenotypes that retain the pluripotent potential of undifferentiated embryonic stem cells may form teratomas when administered to a subject, see, e.g., Thomson 1998 Science 282:1145. Other extraneous phenotypes may interfere with the efficacy of the target phenotype merely by diluting the number of cells of the targeted phenotype thereby reducing the overall efficacy of the cell preparation. Accordingly, there is a need to reduce the number of cells having an extraneous phenotype found in a population of cells comprising the targeted differentiated progeny of pPS cells. There is an additional need for populations of differentiated progeny of pPS cells that have a minimal number of cells of an extraneous phenotype for use in therapeutic, diagnostic and/or research applications. Various embodiments of the invention described herein meet these needs and other needs as well.